Typically, gas masks are used to minimize human casualties caused by an attack of chemical weapons from the enemy in wartime. As illustrated in FIG. 1, a gas mask 100 has a structure in which noxious gases flowing in from the outside are removed by a canister 110 attached thereto so as to enable a wearer to inhale innoxious air only. Multipurpose gas masks for minimizing human casualties resulting from various noxious gases occurring in a war as well as a fire have recently been released in the market.
The canister 110 used in the gas mask 100 includes an absorbent such as activated carbon that chemically adsorbs or decomposes the noxious gases, and filter paper that physically filters particulate substances, and can thus remove the noxious gases in a chemical/physical way.
However, due to the restriction of a physical size of the canister 110, one canister 110 is restricted in capacity capable of removing the noxious gases. As such, when the gas mask is used in prolonged exposure to the noxious gases, an extra canister must be prepared.
If a purifying function of the canister 110 attached to the gas mask 100 is lost without the extra canister, the noxious gases flow into the gas mask 100, and thus a wearer who wears the gas mask 100 may fall into a dangerous situation.